#include <iostream>
#include <vector>
using namespace std;

// 已知
int n;
// 未知
vector<string> a;

int main()
{
    cin >> n;
    for (int i = 0; i < n; ++i)
    {
        a.push_back(string(n, '.'));
    }
    for (int i = 0; i < n; ++i)
    {
        int j = n - i;
        for (int k = i; k < j; ++k)
        {
            for (int f = i; f < j; ++f)
            {
                a[k][f] = i % 2 ? '.' : '#';
            }
        }
        cout << a[i] << endl;
    }
    return 0;
}